Determination of trace vanadium by adsorptive stripping voltammetry at a carbon paste electrode

A method for the voltammetric determination of vanadium using a carbon paste electrode (CPE) was described. The new procedure is based on the adsorptive accumulation of the V(V)-alizarin red S(ARS) complex onto the surface of the CPE, followed by the electrochemical reduction of adsorbed species. The optimal experimental conditions include the use of 0.10 mol/L acetate buffer (pH 5.1), 1.0 x 10(-5) mol/L ARS, an accumulation potential of -0.10 V (versus SCE), an accumulation time of 2 min, a scan rate of 200 mV/s and a second-order derivative linear scan mode. The reduction peak for the complex appears at -0.52 V. The peak current is proportional to the concentration of V(V) over the range of 0.10 - 15.0 mu g/L, and the detection limit is 0.04 mu g/L for a 2 min adsorption time. The relative standard deviations(n = 8) for 2.0 and 0.50 mu g/L V(V) are 3.1 and 4.7%, respectively The proposed method was applied to the determination of vanadium in water samples.